Dietary crude protein time-dependently modulates the bacterial community and metabolites and changes dietary nutrient efficiency in growing pigs

The reduced nutrient digestibility of low-protein (LP) diets has been shown to be caused by the weakened fermentative capacity of the post-gut flora. The dynamic regulation of dietary protein contents on post-gut microbial population and fermentative metabolism is unclear. Twelve growing barrows (19.9 ± 0.8 kg) fitted with a T-cannula at the blind end of the cecum were randomly administered a high-protein (HP, 21.5% crude protein [CP]) diet or an LP (15.5% CP) diet for 28 d. The cecal content and feces were collected at d 1, 14, and 28 of the experiment for microflora structures and metabolite concentrations analysis. The nutrient digestibility coefficient and plasma biochemical parameters were also determined. Compared with the HP treatment, the LP treatment showed decreased plasma urea nitrogen concentration and apparent total tract digestibility of dry matter, gross energy, and CP (P < 0.01). In addition, urinary nitrogen losses, total nitrogen losses, and daily nitrogen retention in the LP treatment were lower than those in the HP treatment (P < 0.01), and the nitrogen retention-to-nitrogen intake ratio in the LP treatment was increased (P < 0.01). The HP group showed increased cecal total short-chain fatty acids (SCFA) concentration and fecal propionate, butyrate, and total SCFA concentrations (P < 0.05) on d 14 and 28, which may be mainly related to the elevated abundance of SCFA-producing bacteria, such as Ruminococcus, Lactobacillus, and Prevotella (P < 0.05). Probiotics, such as Bifidobacterium, Bacteroidales S24-7, and Rikenella, enriched in the LP treatment possibly contributed to reduced plasma endotoxin content. The differences in the abundances of almost all the above-mentioned flora appeared on d 28 but not d 14. Likewise, differences in the Simpson and Shannon indices and clustering patterns of the microbiota between treatments were also only observed on d 28. To sum up, in a time-dependent manner, the LP diet increased probiotics with gut-improving functions and decreased SCFA-producing bacteria, which may cause enhanced intestine health and reduced nutrient digestibility.

Effects of a low-protein nutritional formula with dietary counseling in older adults with chronic kidney disease stages 3-5: a randomized controlled trial

BACKGROUND

Although combining a low-protein diet (LPD) with oral nutritional supplements increases treatment adherence and nutritional status in patients with chronic kidney disease (CKD), the effect of this combination approach in older adults remains unclear. This study examined the impact of a 6% low-protein formula (6% LPF) with diet counseling in older adults with stage 3-5 CKD.

METHODS

In this three-month randomized controlled study, 66 patients (eGFR < 60 mL/min/1.73 m2, non-dialysis, over 65 years of age) were randomly assigned to an intervention group (LPD plus a 6% LPF) or control group (LPD alone). The 6% LPF comprised 400 kcal, 6 g of protein, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and various micronutrients. All data were collected at baseline and after three months, including physical performance based on hand grip strength (HGS) and gait speed, nutritional status using Mini Nutritional Assessment-Short Form (MNA-SF) scores, body composition through bioelectrical impedance analysis, and dietary intake from 24-h dietary records.

RESULTS

This study incorporated 47 participants (median age, 73; median eGFR, 36 ml/min/1.73 m2; intervention group: 24; control group: 23). The intervention group exhibited significant differences in HGS and gait speed, and micronutrient analysis revealed significantly higher monounsaturated fatty acids (MUFA), EPA, DHA, calcium, iron, zinc, copper, thiamine, riboflavin, niacin, B6, B12, and folic acid intake than the control group. MNA-SF scores, macronutrient intake, and body composition did not differ significantly between the two groups.

CONCLUSIONS

Compared to LPD counseling alone, an LPD prescription with 6% LPF in older adults with CKD stages 3-5 helped relieve physical deterioration and increased micronutrient intake after three months.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05318014 (retrospectively registered on 08/04/2022).

An investigation of low-protein diets' qualification rates and an analysis of their short-term effects for patients with CKD stages 3-5: a single-center retrospective cohort study from China

BACKGROUND

The feasibility and efficacy of low-protein diets (LPD) treatment in chronic kidney disease (CKD) is controversial. Based on the characteristics of the Chinese diet, we observe the qualification rates and short-term clinical effects of LPD for CKD patients in our center.

METHODS

This is a retrospective cohort study. CKD stages 3-5 patients who were regularly followed up 5 times (over 2 years) and treated with LPD were included. We collected clinical data to observe the changes in LPD qualification rates and divided patients into LPD and non-LPD group according to the average dietary protein intake (DPI) of 5 follow-up time points and compared the changes in primary and secondary outcome measures between the two groups.

RESULTS

We analyzed data from 161 eligible CKD stages 3-5 patients. From baseline to the 5th follow-up time point, the LPD qualification rates of all patients were 11.80%, 35.40%, 47.82%, 53.43% and 54.04%, respectively. For primary outcome measures, the urine protein/creatinine ratio (UPCR) decreased more in the LPD group than in the non-LPD group [Median (interquartile range, IQR) of the difference between the 5th follow-up time point and baseline: 0.19 (- 0.01-0.73) vs. 0.10 (- 0.08-0.27), P < 0.001]. We constructed three classes of mixed linear models (model I, II, III). The UPCR slopes were all negative in the LPD group and positive in the non-LPD group (P < 0.001). Meanwhile, in model I, the estimate glomerular filtration rate(eGFR) decline slope in the LPD group was lower than that in the non-LPD group [slope (standard error): - 1.32 (0.37) vs. - 2.35 (0.33), P = 0.036]. For secondary outcome measures, body mass index (BMI) triglycerides (TG), body weight, and fat free mass (FFM) showed stable statistical differences in the comparison of LPD and non-LPD groups, with greater declines in the former.

CONCLUSION

The results of this study suggest that LPD treatment can reduce UPCR in patients with CKD stages 3-5, and may also delay the decline in eGFR. Meanwhile, it also reduces BMI, TG, body weight, and FFM, thus the need to prevent malnutrition in clinical implementation.

Nutritional status and the risk of malnutrition in older adults with chronic kidney disease - implications for low protein intake and nutritional care: A critical review endorsed by ERN-ERA and ESPEN

Increased life expectancy is posing unprecedented challenges to healthcare systems worldwide. These include a sharp increase in the prevalence of chronic kidney disease (CKD) and of impaired nutritional status with malnutrition-protein-energy wasting (PEW) that portends worse clinical outcomes, including reduced survival. In older adults with CKD, a nutritional dilemma occurs when indications from geriatric nutritional guidelines to maintain the protein intake above 1.0 g/kg/day to prevent malnutrition need to be adapted to the indications from nephrology guidelines, to reduce protein intake in order to prevent or slow CKD progression and improve metabolic abnormalities. To address these issues, the European Society for Clinical Nutrition and Metabolism (ESPEN) and the European Renal Nutrition group of the European Renal Association (ERN-ERA) have prepared this conjoint critical review paper, whose objective is to summarize key concepts related to prevention and treatment of both CKD progression and impaired nutritional status using dietary approaches, and to provide guidance on how to define optimal protein and energy intake in older adults with differing severity of CKD. Overall, the authors support careful assessment to identify the most urgent clinical challenge and the consequent treatment priority. The presence of malnutrition-protein-energy wasting (PEW) suggests the need to avoid or postpone protein restriction, particularly in the presence of stable kidney function and considering the patient's preferences and quality of life. CKD progression and advanced CKD stage support prioritization of protein restriction in the presence of a good nutritional status. Individual risk-benefit assessment and appropriate nutritional monitoring should guide the decision-making process. Higher awareness of the challenges of nutritional care in older adult patients with CKD is needed to improve care and outcomes. Research is advocated to support evidence-based recommendations, which we still lack for this increasingly large patient subgroup.

Economic Analysis of a Ketoanalogue-Supplemented Very Low-Protein Diet in Patients With Chronic Kidney Disease in Taiwan and Thailand

OBJECTIVE

A vegetarian very low-protein diet (VLPD) supplemented with ketoanalogues of essential amino acids Ketoanalogue-supplemented very low-protein diet (sVLPD) delays dialysis initiation in patients with chronic kidney disease (CKD). In this cost-effectiveness analysis, we compare an sVLPD with a conventional low-protein diet (LPD) in patients with CKD stage 4-5 using data from Taiwan and Thailand.

DESIGN AND METHODS

A Markov model simulated health outcomes and care costs in patients receiving an sVLPD (0.3-0.4 g/kg-day, vegetarian diet) supplemented with ketoanalogues (1 tablet/5 kg-day) or an LPD (0.6 g/kg-day, mixed proteins). Health state transition probability and resource cost inputs were based on published literature and local sources, respectively.

RESULTS

An sVLPD increased survival and quality-adjusted life years (QALYs) at a lower cost than an LPD. Total cost of care in Taiwan was 2,262,592.30 New Taiwan dollars (NTD) (68,059.35 EUR) with an LPD and 1,096,938.20 NTD (32,996.18 EUR) with an sVLPD (difference -1,165,654.10 NTD; -35,063.17 EUR). Total cost of care in Thailand was 500,731.09 Thai baht (THB) (14,584.12 EUR) with an LPD and 421,019.22 THB (12,262.46 EUR) with an sVLPD (difference -79,711.86 THB; -2,321.66 EUR).

CONCLUSION

A ketoanalogue-supplemented vegetarian sVLPD increased QALYs and lowered lifetime care costs versus an LPD in patients with predialysis CKD in Taiwan and Thailand. These data, together with the new KDOQI Guidelines for nutrition in CKD, support dietary intervention using ketoanalogue-supplemented vegetarian sVLPDs to prevent CKD progression and postpone dialysis as a cost-effective approach, with beneficial effects for patients and health care providers.

Role of liver AMPK and GCN2 kinases in the control of postprandial protein metabolism in response to mid-term high or low protein intake in mice

PURPOSE

Protein synthesis and proteolysis are known to be controlled through mammalian target of rapamycin, AMP-activated kinase (AMPK) and general control non-derepressible 2 (GCN2) pathways, depending on the nutritional condition. This study aimed at investigating the contribution of liver AMPK and GCN2 on the adaptation to high variations in protein intake.

METHODS

To evaluate the answer of protein pathways to high- or low-protein diet, male wild-type mice and genetically modified mice from C57BL/6 background with liver-specific AMPK- or GCN2-knockout were fed from day 25 diets differing in their protein level as energy: LP (5%), NP (14%) and HP (54%). Two hours after a 1 g test meal, protein synthesis rate was measured after a ¹³C valine flooding dose. The gene expression of key enzymes involved in proteolysis and GNC2 signaling pathway were quantified.

RESULTS

The HP diet but not the LP diet was associated with a decrease in fractional synthesis rate by 29% in the liver compared to NP diet. The expression of mRNA encoding ubiquitin and Cathepsin D was not sensitive to the protein content. The deletion of AMPK or GCN2 in the liver did not affect nor protein synthesis rates and neither proteolysis markers in the liver or in the muscle, whatever the protein intake. In the postprandial state, protein level alters protein synthesis in the liver but not in the muscle.

CONCLUSIONS

Taken together, these results suggest that liver AMPK and GCN2 are not involved in this adaptation to high- and low-protein diet observed in the postprandial period.

Dietary Protein and Fiber Affect Gut Microbiome and Treg/Th17 Commitment in Chronic Kidney Disease Mice

BACKGROUND

Patients with chronic kidney disease (CKD) have dysbiosis, dysmetabolism, and immune dysregulation. Gut microbiome plays an important role shaping the immune system which is an important modulator of CKD progression.

METHODS

We compared the effect of a diet low in protein and high in fiber (LP-HF; n = 7) to that of diet rich in protein, but low in fiber (HP-LF; n = 7) on gut microbiome and T-cell commitment in male CKD (Alb/TGF-β1) mice. The gut microbiomes of these mice were subjected to 16S rRNA taxonomic profiling at baseline, 6 weeks and 12 weeks of the study.

RESULTS

The LP-HF diet was associated with an increase in Butyricicoccus pullicaecorum BT, a taxon whose functions include those closely related to butyric acid synthesis (Kendall's W statistic = 180 in analysis of microbiome composition). HP-LF diet was associated with increased abundance of two predominantly proteolytic bacterial strains related to Parabacteroides distasonis (W statistic = 173), Mucispirillum schaedleri, and Bacteroides dorei (W statistic = 192). Pathway analysis suggested that the LP-HF diet induced carbohydrate, lipid, and butyrate metabolism. As compared with HP-LF mice, LP-HF mice had 1.7-fold increase in CD4+Foxp3+Treg cells in spleen and 2.4-fold increase of these cells in peripheral blood. There was an 87% decrease in percentage of CD4+ Th17 + cells in spleen and an 85% decrease in peripheral blood, respectively, in LP-HF mice compared to the HP-LF mice.

CONCLUSION

The LP-HF diet promotes the proliferation of saccharolytic bacteria and favors T-cell commitment toward Treg cells in a CKD mouse of model. Clinical significance of the finding needs to be further investigated.

Risk of all-cause mortality in subjects with varying degrees of renal impairment with or without dietary protein restriction

BACKGROUND AND OBJECTIVE

Low-protein diet (less than 0.8g/kg/day) has been practiced in the management of chronic kidney disease (estimated glomerular filtration rate [eGFR]<60ml/min/1.73m² or urine albumin-to-creatinine ratios [UACR] ≥30mg/g) for decades. However, its effect on all-cause mortality is unclear. We investigated the association between a low-protein intake and all-cause mortality in subjects with varying degrees of renal impairment.

MATERIALS AND METHODS

We analyzed participants in the National Health and Nutrition Examination Survey (NHANES) from 2003 to 2010. They were divided into four groups according to their eGFR (≥60 or <60ml/min/1.73m²) and UACR (≥30 or <30mg/g). Daily protein intake of the NHANES participants could be assessed using information from the dietary interview questionnaires. The mortality data was retrieved by linking to the National Death Index till the end of 2011. The hazard ratios for all-cause mortality were evaluated by the weighted Cox proportional hazards regression models.

RESULTS

A total of 8093 participants were analyzed. During a median follow-up of 4.7 years, participants with UACR≥30mg/g (with or without eGFR<60ml/min/1.73m²) had a higher risk of all-cause mortality compared with those having UACR<30mg/g and eGFR≥60ml/min/1.73m² (reference group). The higher risk of mortality in participants with UACR≥30mg/g was consistently observed in those with or without a low-protein intake.

CONCLUSIONS

A low-protein intake was not associated with a lower risk of all-cause mortality in subjects with varying degrees of renal impairment.

Low-protein diet is inversely related to the incidence of chronic kidney disease in middle-aged and older adults: results from a community-based prospective cohort study

PURPOSE

Dietary protein intake can modulate renal health. However, the effect of dietary protein restriction on kidney function in the general population remains unclear. This study aimed to examine the association between total protein intake and new-onset chronic kidney disease (CKD) in Korean adults.

METHODS

We included 7339 participants from the Korean Genome and Epidemiology Study. Participants were divided into low-protein diet (LPD, < 0.8 g/kg/day), normal-protein diet (NPD, 0.8-1.3 g/kg/day), and high-protein diet (HPD, > 1.3 g/kg/day) groups. New-onset CKD was defined as two consecutive events of estimated glomerular filtration rate < 60 mL/min/1.73 m². Multivariable Cox hazard regression analysis was conducted to examine the association of total protein intake with new-onset CKD. Subgroup analyses according to diabetes mellitus (DM) status were performed. We performed the same analyses by dividing participants into total protein, plant protein, and animal protein intake tertiles.

RESULTS

During a median follow-up of 13.7 years, 633 (8.7%) participants newly developed CKD. The fully adjusted hazard ratios (HR) with 95% confidence interval (CI) for incident CKD of the LPD and HPD groups compared with the NPD group were 1.49 (1.18-1.87) and 0.63 (0.45-0.87), respectively. The HR (95% CI) of the highest tertile group of plant protein intake for incident CKD was 0.72 (0.54-0.93), compared with that of the lowest tertile group. Similar trends were observed only in the non-DM subgroup, not in the DM subgroup.

CONCLUSION

Protein intake, especially plant proteins, was negatively associated with the incidence of new-onset CKD in middle-aged and older Korean adults.

Different dietary starch patterns in low-protein diets: effect on nitrogen efficiency, nutrient metabolism, and intestinal flora in growing pigs

Background

Protein releases amino acids faster than starch releases glucose in digestive tract of pigs fed low-protein (LP) diets. Poor synchronization of dietary glucose and amino acids supply leads to compromised nitrogen efficiency. Dietary starch patterns modulation may improve this situation.

Methods

Growing barrows (29.7 ± 2.0 kg) were randomly allotted into 5 dietary treatments with LP diets consisting of different purified starches. Treatments included: waxy corn starch (W LP), corn starch + waxy corn starch (C + W LP), corn starch (C LP), pea starch + waxy corn starch (P + W LP) and pea starch (P LP). In the experiment, growth performance, protein deposition, nutrient metabolism, and fecal microbial community of pigs were investigated. In vitro starch digestion was used for predicting the in vivo glucose response.

Results

Dietary starch in vitro glucose release profile was determined by starch source and the ratio of amylopectin and amylose. C + W LP treatment showed decreased total nitrogen excretion and plasma citrulline concentration and improved plasma leptin concentration among treatments (P < 0.05). Besides, the highest nitrogen apparent biological value, whole-body protein deposition and growth performance and lowest urinary nitrogen excretion were also observed in C + W LP treatment. Compared with the other groups, C + W LP and C LP showed increased plasma pyruvate, IGF-1, and lipase concentrations (P < 0.05). The W LP group presented dramatically increased plasma alanine and urea nitrogen concentration and decreased aldolase and leptin concentrations (P < 0.05). Dietary starch patterns did not make an impact on bacterial richness and diversity, but changed the taxonomic and functional structures of the microbial communities. Microbial protein fermentation product (isobutyrate and isovalerate) presented increased in P LP treatments compared with the other treatments (P < 0.05).

Conclusions

Dietary starch patterns modulation can regulate dietary glucose release profile, nutrient metabolism, protein turnover, and fecal microbial fermentation in pigs. The optimal dietary glucose release profile effectively strengthened whole-body protein deposition and improve nitrogen efficiency and growth performance in growing pigs fed LP diets.

Use of low-protein staple foods in the dietary management of patients with stage 3-4 chronic kidney disease: a prospective case-crossover study

OBJECTIVE

Maintaining a low-protein diet (LPD) is important for patients with chronic kidney disease (CKD) to delay renal degradation and alleviate clinical symptoms. For most patients with CKD, it is difficult to maintain the necessary low level of dietary protein intake (DPI). To improve the current dietary management of CKD, we conducted an intervention study by administering low-protein staple foods (LPSF).

DESIGN AND METHODS

We conducted a prospective case-crossover study among 25 patients with stage 3-4 CKD. During the initial 12 weeks of the study, we instructed the patients regarding a standard LPD according to the recommendations of a renal dietitian. In the second stage of the study, we requested the patients taking low-protein rice or low-protein flour (250 g/d) as an LPSF diet instead of regular staple food daily, and followed these patients up for 12 weeks. We compared the DPI, dietary energy intake (DEI), normalized protein equivalent of total nitrogen appearance (nPNA), serum creatinine levels, and nutritional index between baseline and the end of the study.

RESULTS

We found no change in dietary variables among the patients during the first 12 weeks of the LPD. After subjecting them to an LPSF diet, the corresponding variables showed a pronounced change. The patients' DPI decreased from 0.88 ± 0.20 to 0.68 ± 0.14 g/kg/d (P < 0.01) and the nPNA value decreased from 0.99 ± 0.18 to 0.87 ± 0.19 g/kg/d (P < 0.01). The high biological value protein intake proportion increased from 42% (baseline) to 57% (P < 0.01) during the 24 weeks. No variation was found in the measured DEI (28.0 ± 5.8 vs 28.6 ± 5.4 kcal/kg/d), nutrition assessment, or renal function and serum creatinine levels.

CONCLUSION

Our prospective case-crossover study demonstrated that an LPSF diet can help patients with stage 3-4 CKD reduce DPI and nPNA values, improve the proportion of highly bioavailable proteins, ensure adequate calorie intake, and avoid malnutrition. An LPSF diet is an effective and simple therapy for patients with stage 3-4 CKD.

Low-protein diets supplemented with methionine and lysine alter the gut microbiota composition and improve the immune status of growing lambs

Feeding low-protein (LP) diets with essential amino acids could be an effective strategy for ruminants from economic, health and environmental perspectives. This study was conducted to investigate the effects of rumen-protected methionine and lysine (RML) in the LP diet on growth performance, innate immunity, and gut health of growing lambs. After 15 days of adaption, sixty-three male Hulunbuir lambs aged approximately 4 months were allotted to three dietary groups and each group had three pens with seven lambs for 60 days. The dietary treatments were as follows: a normal protein diet (14.5% CP, positive control; NP), LP diet (12.5% CP, negative control; LP), and LP diet with RML (12.5% CP, LP + RML). Lambs fed with LP + RML diet showed improved villus architecture and gut barrier function than those fed with the other two diets. The mRNA expressions of interleukin-1β, tumor necrosis factor-α, interferon-γ, toll-like receptor-4, and myeloid differentiation primary response 88 were downregulated in most regions of the intestinal segments by feeding the LP + RML diet. Compared with the NP diet, feeding lambs with the LP diet increased the abundance of Candidatus_Saccharimonas in all regions of the intestinal tract and reversed by feeding the LP + RML diet. Lambs in the LP + RML diet group had lower abundance of Erysipelotrichaceae_UCG-009 and Clostridium_sensu_stricto_1 than those in the LP diet group. The results showed that supplementing RML in the LP diet exhibited beneficial effects on host immune function, intestinal mucosal integrity, and microbiota composition. KEY POINTS: • Adding methionine and lysine in a low-protein diet improve the intestinal mucosal growth and integrity. • Feeding a low-protein diet with methionine and lysine enhance the innate immune status. • Adding methionine and lysine in a low-protein diet alter the intestinal microbiota composition.

Low-protein diet accelerates wound healing in mice post-acute injury

BACKGROUND

Wound healing processes are influenced by macronutrient intake (protein, carbohydrate and fat). The most favourable diet for cutaneous wound healing is not known, although high-protein diets are currently favoured clinically. This experimental study investigates the optimal macronutrient balance for cutaneous wound healing using a mouse model and the Geometric Framework, a nutrient modelling method, capable of analyzing the individual and interactive effects of a wide spectrum of macronutrient intake.

METHODS

Two adjacent and identical full-thickness skin excisions (1 cm2) were surgically created on the dorsal area of male C57BL/6 mice. Mice were then allocated to one of 12 high-energy diets that varied in protein, carbohydrate and fat content. In select diets, wound healing processes, cytokine expression, energy expenditure, body composition, muscle and fat reserves were assessed.

RESULTS

Using the Geometric Framework, we show that a low-protein intake, coupled with a balanced intake of carbohydrate and fat is optimal for wound healing. Mice fed a low-protein diet progressed quickly through wound healing stages with favourable wound inflammatory cytokine expression and significantly accelerated collagen production. These local processes were associated with an increased early systemic inflammatory response and a higher overall energy expenditure, related to metabolic changes occurring in key macronutrient reserves in lean body mass and fat depots.

CONCLUSIONS

The results suggest that a low-protein diet may have a greater potential to accelerate wound healing than the current clinically used high-protein diets.

Effects of ketoanalogues on skeletal muscle mass in patients with advanced chronic kidney disease: real-world evidence

OBJECTIVE

Ketoanalogue (KA) supplementation in patients with chronic kidney disease (CKD) on a restricted protein diet has been shown to maintain their nutritional status in clinical trials. However, a gap existed between the findings of the clinical trials and the real-world practice. The aim of this prospective observational study was to evaluate the KA effect on skeletal muscle mass in patients with stage 4-5 CKD.

METHODS

Among 170 patients with CKD screened, 148 were recruited. Patients were defined as KA or non-KA users. During a 12-mo follow-up, skeletal muscle and body fat mass were measured via bioelectrical impedance analysis at baseline, 6 mo (n = 108), and 12 mo (n = 85).

RESULTS

Among the patients (mean age, 66.5 ± 12.9 y), KA users tended to maintain skeletal muscle and body fat mass, whereas non-KA users had a significantly reduced muscle mass (P = 0.011) and body fat gain (P = 0.004). Stratified by median age, in patients ≥68 y of age, non-KA users yielded the most significant muscle mass reduction and fat mass gain, whereas KA users revealed no changes in skeletal muscle and fat mass.

CONCLUSION

In real-world practice, we concluded that KA supplementation favorably prevents skeletal muscle mass loss and fat mass gain in elderly patients with stage 4-5 CKD.

Typical gut indigenous bacteria in ICR mice fed a soy protein-based normal or low-protein diet

For patients with inflammatory bowel disease, cow’s milk allergy, and lactose intolerance, soymilk is a potential alternative to cow’s milk. In this study, we aimed to identify the effects of a soy protein-based low-protein diet on the body and organ weights and the gut microbiome of six-week-old mice fed a diet containing 20% (SP) or 5% (LP) soy protein for 14 days via 16S rRNA (V4) amplicon sequencing. Body weight gain (growth) and liver, spleen, and fat tissue weight were significantly suppressed by the LP diet. Operational taxonomic unit numbers and α-diversity were lower in the LP group than in the SP group. A principal coordinate analysis revealed differences in the gut microbiome compositions of SP and LP mice. The abundances of caecal Roseburia sp., Alistipes sp., and bacteria from the family Muribaculaceae were lower in the LP group than in the SP group. In contrast, the abundance of Desulfovibrionaceae, which is positively correlated with inflammation, was higher in the LP group than in the SP group. These results differed from the effects of a milk casein-based low-protein diet (reported previously). Based on these findings, we conclude that the undesirable effects of a low-protein diet and/or protein deficiency are related to changes in the gut microbiome composition and may differ depending on the kind of proteins used.

•

Six-week-old ICR mice were fed a diet containing 20% (SP) or 5% (LP) soy protein for 14 days.

•

Body weight gain and liver, spleen, and fat tissue weight were significantly suppressed by the LP diet.

•

Caecal Roseburia sp., Alistipes sp., and bacteria from the family Muribaculaceae was lower in the LP.

•

Desulfovibrionaceae, which is positively correlated with inflammation, was higher in the LP group.

Serine-to-glycine ratios in low-protein diets regulate intramuscular fat by affecting lipid metabolism and myofiber type transition in the skeletal muscle of growing-finishing pigs

Serine and glycine are 2 of the first-affected nonessential amino acids in low crude protein (CP) diets for pigs. Therefore, we explored the effects of different dietary serine-to-glycine ratios on growth performance and lipid metabolism in growing-finishing pigs. A total of 160 crossbred healthy barrows, with a similar body weight of around 59.50 kg, were randomly allotted into 1 of 5 treatments (8 pens per treatment and 4 pigs per pen). The serine-to-glycine ratios of the 5 dietary treatments were as follows: diet A (NORMAL group), 1.18:1 (16% CP); diet B (LOW group), 1.2:1 (12% CP); diet C (S2G1 group), 2:1 (12% CP); diet D (S1G2 group), 1:2 (12% CP); and diet E (S1G1 group), 1:1 (12% CP).We found that the pigs fed a low CP diet (12% CP), when maintaining serine-to-glycine ratio at 1:2 and a total amount of 1.44%, had the same average daily gain as the pigs fed a normal CP diet (16% CP) (P > 0.05), but they had increased intramuscular fat (P < 0.05). Furthermore, they exhibited higher expression of genes involved in lipid oxidation (P < 0.05), which was regulated by modulating methylation levels in the promoters of acyl-CoA oxidase 1 (ACOX1) and acyl-CoA dehydrogenase medium chain (ACADM). When compared with the pigs fed a normal CP diet, these pigs had more oxidative myofibers (P < 0.05), which were regulated by AMPK-PGC-1α and Calcineurin-MEF2/NFAT pathways in a coordinated manner. Our findings suggested that a dietary serine-to-glycine ratio of 1:2 is beneficial for improving meat quality in pigs fed a low CP diet.

Maternal protein restriction impairs nutrition and ovarian histomorphometry without changing p38MAPK and PI3K-AKT-mTOR signaling in adult rat ovaries

AIMS

Because an adequate protein supply is detrimental for the maintenance of folliculogenesis and ovulation, we evaluated the impact of maternal low protein diet on nutritional parameters, estrous cycle, ovarian histomorphometry, and on the expression of metabolic and survival signaling molecules in different follicular stages.

MAIN METHODS

Twenty Wistar pregnant rats were divided into two groups: the normoprotein (NP) group, composed of animals that received 17% protein, and a low-protein (LP) group, composed of animals that received 6% protein during gestation and lactation period. After weaning, female rats were fed with standard diet until the 120-days-old.

KEY FINDINGS

LP animals showed reduced body mass index, total body weight, energy intake, feed efficiency, and visceral fat. The ovarian tissue presented vascular congestion and fat accumulation in the medulla, followed by a significant reduction in the amount of primordial and primary follicles. In addition, the number of atretic follicles was higher in LP than in NP animals. Maternal undernutrition also resulted in increased levels of estradiol (E2) and progesterone (P4) while testosterone (T) was unchanged in the offspring. Although discrete changes in p38MAPK and in PI3K-AKT-mTOR immunostaining were observed in the ovarian follicles and corpus luteum in LP, no differences were found at their protein levels.

SIGNIFICANCE

Maternal protein restriction alters estrous cycle and histomorphometry of the offspring's ovary without changing the levels of intracellular regulatory molecules in adulthood. These morphofunctional changes may alter reproductive performance in female offspring, highlighting maternal dietary conditions as an important factor for offspring reproductive health.

Diabetic Kidney Disease Benefits from Intensive Low-Protein Diet: Updated Systematic Review and Meta-analysis

A dietary protein intake (DPI) of between 0.6 and 0.8 g protein per kilogram body weight per day (g/kg/day) is frequently recommended for adults with moderate-to-advanced chronic kidney disease (CKD). However, evidence on whether patients with diabetic kidney disease (DKD) actually benefit from a DPI of ≤ 0.8 g/kg/day and from a low-protein diet (LPD) at CKD stages 1-3 has not been consistent. We systematically searched MEDLINE, EMBASE, Cochrane Library, Web of Knowledge, as well as the bibliographies of articles identified in the search, for eligible randomized controlled trials that had investigated the effects of LPD (prescribed DPI < 0.8 g/kg/day) versus control diet on the progression of DKD. Nine trials that included 506 participants and follow-up periods varying from 4.5 to 60 months were included in the subsequent systematic review and meta-analysis. The data showed that patients with DKD who consumed < 0.8 g protein/kg/day had a significantly reduced decline in glomerular filtration rate (GFR) (mean difference [MD] 22.31 mL/min/1.73 m², 95% confidence interval [CI] 17.19, 27.42; P  < 0.01) and a significant decrease in proteinuria (standard mean difference [SMD] - 2.26 units, 95% CI - 2.99, - 1.52; P  < 0.001) versus those on the control diet. The benefits of LPD to patients with DKD at CKD stages 1-3 were a markedly decreased proteinuria (SMD - 0.96 units, 95% CI - 1.81, - 0.11; P  = 0.03) and slight but significant decreases in glycated hemoglobin (- 0.42%) and cholesterol levels (- 0.22 mmol/L). Our meta-analysis indicated that a DPI of < 0.8 g/kg/day was strongly associated with a slow decline in GFR and decreased proteinuria in the patients with DKD. Patients with CKD stages CKD 1-3 benefited from LPD in terms of a marked decrease of proteinuria and slight but significant improvements in lipid and glucose control.

Low-arginine and low-protein diets induce hepatic lipid accumulation through different mechanisms in growing rats

Background

Dietary protein deficiency and amino acid imbalance cause hepatic fat accumulation. We previously demonstrated that only arginine deficiency or total amino acid deficiency in a diet caused significant hepatic triglyceride (TG) accumulation in young Wistar rats. In this study, we explored the mechanisms of fatty liver formation in these models.

Methods

We fed 6-week-old male Wistar rats a control diet (containing an amino acid mixture equivalent to 15% protein), a low-total-amino acid diet (equivalent to 5% protein; 5PAA), and a low-arginine diet (only the arginine content is as low as that of the 5PAA diet) for 2 weeks.

Results

Much greater hepatic TG accumulation was observed in the low-arginine group than in the low-total-amino acid group. The lipid consumption rate and fatty acid uptake in the liver did not significantly differ between the groups. In contrast, the low-total-amino acid diet potentiated insulin sensitivity and related signaling in the liver and enhanced de novo lipogenesis. The low-arginine diet also inhibited hepatic very-low-density lipoprotein secretion without affecting hepatic insulin signaling and lipogenesis.

Conclusions

Although the arginine content of the low-arginine diet was as low as that of the low-total-amino acid diet, the two diets caused fatty liver via completely different mechanisms. Enhanced lipogenesis was the primary cause of a low-protein diet-induced fatty liver, whereas lower very-low-density lipoprotein secretion caused low-arginine diet-induced fatty liver.

Effects of adding sodium dichloroacetate to low-protein diets on nitrogen balance and amino acid metabolism in the portal-drained viscera and liver of pigs

Background

Identifying regulatory measures to promote glucose oxidative metabolism while simultaneously reducing amino acid oxidative metabolism is one of the foremost challenges in formulating low-protein (LP) diets designed to reduce the excretion of nitrogen-containing substances known to be potential pollutants. In this study, we investigated the effects of adding sodium dichloroacetate (DCA) to a LP diet on nitrogen balance and amino acid metabolism in the portal-drained viscera (PDV) and liver of pigs.To measure nitrogen balance, 18 barrows (40 ± 1.0 kg) were fed one of three diets (n = 6 per group): 18% crude protein (CP, control), 13.5% CP (LP), and 13.5% CP + 100 mg DCA/kg dry matter (LP-DCA). To measure amino acid metabolism in the PDV and liver, 15 barrows (40 ± 1.0 kg) were randomly assigned to one of the three diets (n = 5 per group). Four essential amino acids (Lys, Met, Thr, and Trp) were added to the LP diets such that these had amino acid levels comparable to those of the control diet.

Results

The LP-DCA diet reduced nitrogen excretion in pigs relative to that of pigs fed the control diet (P < 0.05), without any negative effects on nitrogen retention (P > 0.05). There were no differences between the control and LP-DCA groups with respect to amino acid supply to the liver and extra-hepatic tissues in pigs (P > 0.05). The net release of ammonia into the portal vein and production rate of urea in the liver of pigs fed the LP-DCA diet was reduced relative to that of pigs fed the control and LP diets (P < 0.05).

Conclusion

The results indicated that addition of DCA to a LP diet can efficiently reduce nitrogen excretion in pigs and maximize the supply of amino acids to the liver and extra-hepatic tissues.

Excessive BCAA regulates fat metabolism partially through the modification of m6A RNA methylation in weanling piglets

Background

Fat percentage and distribution in pigs are associated with their productive efficiency and meat quality. Dietary branched-chain amino acids (BCAA) regulate fat metabolism in weanling piglets with unknown mechanism. It is reported that N6-methyl-adenosine (m⁶A) is involved in fat metabolism in mice. The current study was designed to investigate the relationship between dietary branched-chain amino acids and fat metabolism through N6-methyl-adenosine (m⁶A) in weanling piglets.

Methods

A total of 18 healthy crossbred weaned piglets (Duroc × Landrace × Large White, 10.45 ± 0.41 kg) were divided into 3 treatments and were fed the low BCAA dose diet (L-BCAA), the normal dose BCAA diet (N-BCAA), or the high dose BCAA (H-BCAA) diet for 3 weeks.

Results

Our results show that compared with the N-BCAA group, the L-BCAA group had higher concentration of serum leptin (P < 0.05), while the H-BCAA group had lower concentration of serum adiponectin (P < 0.05). Fatty acid synthesis in pigs from the H-BCAA group was lower than those from the N-BCAA group with the down-regulation of lipogenic genes (ACACA, FASN, PPAR-r, SREBP-1c in ventral and dorsal fat, SREBP-1c in liver) and up-regulation of lipolysis genes (HSL, ATGL, CPT-1A, FABP4 in ventral fat, HSL in liver) (P < 0.05). Similarly, fatty acid synthesis in pigs from the L-BCAA group was also lower than those from the N-BCAA group with the decrease of lipogenic genes (ACACA in ventral, ACACA and FASN in dorsal fat, ACACA, FASN, SREBP-1c in liver) and the increase of lipolysis genes (ATGL, CPT-1A CD36, FABP4 in ventral fat and HSL, ATGL, CPT-1A in dorsal fat, CPT-1A) (P < 0.05). Feeding H-BCAA diet significantly reduced total m⁶A levels in ventral and dorsal fat and liver tissues (P < 0.05). The decrease of total m⁶A is associated with down-regulation of METTL3, METTL14 and FTO in dorsal fat and METTL3 and FTO in liver (P < 0.05). Decreased m⁶A modification of ACACA and FASN in ventral and dorsal adipose tissues was observed in pig fed with excessive BCAA.

Conclusion

These results suggest that insufficient or excessive BCAA decreased the fat deposition by increasing lipolysis and deceasing lipogenesis in adipose and liver tissues. Dietary excessive BCAA might regulate the process of lipid metabolism partly through the m⁶A RNA methylation.

Low-protein diets supplemented with casein hydrolysate favor the microbiota and enhance the mucosal humoral immunity in the colon of pigs

Background

High-protein diets can increase the colonic health risks. A moderate reduction of dietary crude-protein (CP) level can improve the colonic bacterial community and mucosal immunity of pigs. However, greatly reducing the dietary CP level, even supplemented with all amino acids (AAs), detrimentally affects the colonic health, which may be due to the lack of protein-derived peptides. Therefore, this study evaluated the effects of supplementation of casein hydrolysate (peptide source) in low-protein (LP) diets, in comparison with AAs supplementation, on the colonic microbiota, microbial metabolites and mucosal immunity in pigs, aiming to determine whether a supplementation of casein hydrolysate can improve colonic health under very LP level. Twenty-one pigs (initial BW 19.90 ± 1.00 kg, 63 ± 1 days of age) were assigned to three groups and fed with control diet (16% CP), LP diets (13% CP) supplemented with free AAs (LPA) or casein hydrolysate (LPC) for 4 weeks.

Results

Compared with control diet, LPA and LPC diet decreased the relative abundance of Streptococcus and Escherichia coli, and LPC diet further decreased the relative abundance of Proteobacteria. LPC diet also increased the relative abundance of Lactobacillus reuteri. Both LP diets decreased concentrations of ammonia and cadaverine, and LPC diet also reduced concentrations of putrescine, phenol and indole. Moreover, LPC diet increased total short-chain fatty acid concentration. In comparison with control diet, both LP diets decreased protein expressions of Toll-like receptor-4, nuclear factor-κB, interleukin-1β and tumor necrosis factor-α, and LPC diet further decreased protein expressions of nucleotide-binding oligomerization domain protein-1 and interferon-γ. LPC diet also increased protein expressions of G-protein coupled receptor-43, interleukin-4, transforming growth factor-β, immunoglobulin A and mucin-4, which are indicators for mucosal defense activity.

Conclusions

The results showed that supplementing casein hydrolysate showed beneficial effects on the colonic microbiota and mucosal immunity and barrier function in comparison with supplementing free AAs in LP diets. These findings may provide new framework for future nutritional interventions for colon health in pigs.

Electronic supplementary material

The online version of this article (10.1186/s40104-019-0387-9) contains supplementary material, which is available to authorized users.

Effects of dietary protein intake on renal outcome and mortality in patients with advanced diabetic nephropathy

BACKGROUND

The difficulty of adhering to a low-protein diet is a serious limitation of randomized controlled trials aimed at validating the efficacy of this therapy. In this observational study of patients with diabetic nephropathy, we examined the association of dietary protein intake (DPI) with renal outcome and mortality, taking into account the nutritional status.

METHODS

We conducted a single-center historical cohort study of 449 adult Japanese patients with type 2 diabetes and the urinary albumin-to-creatinine ratio of ≥ 300 mg/g or estimated glomerular filtration rate of < 30 mL/min/1.73 m². DPI was estimated with a formula using nitrogen levels in spot urine and body mass index. Malnutrition was defined as the Geriatric Nutritional Risk Index of ≤ 98. The primary and secondary endpoints were renal replacement therapy (RRT) initiation and mortality before RRT initiation, respectively. The Fine and Gray subdistribution hazard model was used to determine the relative effects of DPI on the respective endpoint.

RESULTS

Decreased DPI was associated with lower incidence of RRT with an adjusted hazard ratio of 0.81 (95% confidence interval: 0.72-0.92, p < 0.001). The interaction between DPI and nutritional status with respect to mortality was significant (p interaction = 0.047). Decreased DPI was a risk factor for mortality in patients with malnutrition (p = 0.009) but not in those without malnutrition (p = 0.559).

CONCLUSIONS

In patients with type 2 diabetic nephropathy, lower DPI was associated with lower incidence of RRT initiation, suggesting beneficial effects of a low-protein diet on kidneys. Conversely, lower DPI might lead to increased mortality in patients with malnutrition.

RNA-Sequencing Analysis of Paternal Low-Protein Diet-Induced Gene Expression Change in Mouse Offspring Adipocytes

Increasing evidence indicates that parental diet affects the metabolism and health of offspring. It is reported that paternal low-protein diet (pLPD) induces glucose intolerance and the expression of genes involved in cholesterol biosynthesis in mouse offspring liver. The aim of the present study was to determine the effect of a pLPD on gene expression in offspring white adipose tissue (WAT), another important tissue for the regulation of metabolism. RNA-seq analysis indicated that pLPD up- and down-regulated 54 and 274 genes, respectively, in offspring WAT. The mRNA expression of many genes involved in lipogenesis was down-regulated by pLPD feeding, which may contribute to metabolic disorder. The expression of carbohydrate response element-binding protein β (ChREBP-β), an important lipogenic transcription factor, was also significantly lower in the WAT of pLPD offspring, which may have mediated the down-regulation of the lipogenic genes. By contrast, the LPD did not affect the expression of lipogenic genes in the WAT of the male progenitor, but increased the expression of lipid oxidation genes, suggesting that a LPD may reduce lipogenesis using different mechanisms in parents and offspring. These findings add to our understanding of how paternal diet can regulate metabolism in their offspring.

Low-protein diet enhances adiponectin secretion in rats

Previous studies including ours have shown that a low-protein diet up-regulates insulin signaling in the liver and muscle and induces fatty liver in rats. Adiponectin is known as an insulin-sensitizing adipocytokine. We, therefore, examined the effect of a low-protein diet on the adiponectin levels in rats. The low-protein diet significantly increased serum adiponectin level. However, mRNA and protein levels of adiponectin in white adipose tissue (WAT) were not changed by the low-protein diet. Since it is known that oligomerization is important to control serum adiponectin level, we examined the population of adiponectin oligomeric forms in WAT and found that low-protein diet did not change it. Despite these events, the amount of its secretion was significantly increased in the adipocytes isolated from WAT of low-protein diet-fed rats. These results indicate that a low-protein diet enhances adiponectin secretion, which is not due to the increased intracellular amount and oligomerization of adiponectin.

Hydroalcoholic extract of Brazilian green propolis modulates inflammatory process in mice submitted to a low protein diet

The occurrence of inflammation and protein malnutrition is an aggravating risk factor for morbidity and mortality in the clinical setting. The green propolis, a natural product made by Apis mellifera bees from Baccharis dracunculifolia resin, has therapeutic potential to modulate chronic inflammation. However, its effect on inflammation in an impaired nutritional status is not known. The aim of this study was to characterize the effects of the administration of the hydroalcoholic extract of the green propolis in the chronic inflammatory process of mice submitted to a low-protein diet. For this, we used the subcutaneous implantation of sponge disks as an inflammatory model and the animals were distributed in the following groups: standard protein diet (12% protein content), control treatment; standard protein diet, propolis treatment; low-protein diet (3% protein content), control treatment; low-protein diet, propolis treatment. Propolis was given daily at a dose of 500 mg/kg (p.o.) during a period of 7 or 15 days. Our main findings show that animals fed with standard protein diet and treated with propolis had low levels of red blood cells, hemoglobin, and hematocrit, with the subsequent reestablishment of these levels, in addition to monocyte count elevation and higher TNF levels after one week of treatment. In the low-protein diet group, the propolis treatment provided a significant recovery in weight and maintenance of total serum protein levels at the end of two weeks of treatment. Histological analysis showed propolis reduced the inflammatory infiltrate in the sponges of both standard and low-protein diet groups. In addition, the propolis extract presented antiangiogenic effect in both groups. Therefore, our data suggests that the hydroalcoholic extract of the green propolis promotes weight recovery and avoid the reduction of protein levels, in addition to inhibit inflammation and angiogenesis in animals fed with a low-protein diet.

Dairy products and chronic kidney disease: protective or harmful? asystematic review of prospective cohort studies

OBJECTIVE

Evidence on the relationship between food sources of protein and progressive decline in renal function in the general population is still controversial. Among the protein-rich foods, dairy products have gained a lot of attention in research on the prevention of metabolic disorders. This systemic review attempted to summarize the findings of prospective cohort studies on the relationship between dairy foods and incident chronic kidney disease (CKD) in the general population.

METHODS

The PubMed, Embase, Scopus, and Web of Science databases were searched from inception up to January 2018 with no restriction on the language of publication. Studies conducted in the general population with consumption of dairy foods as the exposure of interest and with incident CKD and/or decline in renal function as the study outcome were eligible for inclusion in the review.

RESULTS

Of the 391 articles that were extracted through database searching, 7 were included in the review. Of the seven studies, five reported a protective association for dairy consumption, particularly low-fat dairy, against incident CKD or rapid decline in renal function; however, two studies did not find such an association.

CONCLUSION

Despite the limited studies on this topic, findings from the available reports are generally in favor of a positive association between dairy and renal health in the general population. However, further studies are needed to replicate this finding and to determine whether this relationship could be influenced by the fat content and/or the dairy subtypes.

Efficacy of low-protein diet for diabetic nephropathy: a systematic review of randomized controlled trials

Background

A low-protein diet (LPD) is believed to be beneficial in slowing the progression of kidney disease. It is reported that low protein diet can improve protein, sugar and lipid metabolism, and reduce the symptoms and complications of renal insufficiency. However, there has been controversial regarding the effects of protein restriction on diabetic nephropathy (DN).

Objective

To investigate the efficacy of LPD on renal function in patients with type 1 or 2 DN by meta-analysis of randomized controlled trials (RCTs).

Design

PubMed, MEDLINE, EMBASE and China National Knowledge Infrastructure databases were searched. Eleven randomized controlled trials met the inclusion criteria, of which 10 were English and 1 was Chinese. The primary outcome was a change in glomerular filtration rate (GFR). The secondary outcome was a change in proteinuria. Random-effects models were used to calculate the standardized mean difference (SMD) and the corresponding 95% confidence intervals (CI). Subgroup analyses were also performed.

Results

Our research indicated that LPD was not associated with a significant improvement in GFR (1.59 ml · min⁻¹ · 1.73 m⁻², 95% CI -0.57, 3.75, I² = 76%; p = 0.15). This effect was consistent across the subgroups regardless of type of diabetes, course of diabetes and intervention period. Our results also showed that there was no significant difference on improvement of proteinuria in patients of LPD and those in normal-protein diet groups (− 0.48, 95%CI-1.70, 0.74, I² = 94%, p = 0.44). Subgroup analysis revealed that LPD resulted in increased excretion of proteinuria in patients with type 2 diabetes (1.32, 95% CI 0.17, 2.47, I² = 86%, p = 0.02).

Conclusion

The present research showed that LPD was not significantly associated with improvement of renal function in patients with either type 1 or 2 diabetic nephropathy. Although these results do not completely eliminate the possibility that LPD is beneficial for patients with diabetic nephropathy, it does not seem to be significant benefit to renal function.

Gestational low-protein intake enhances whole-kidney miR-192 and miR-200 family expression and epithelial-to-mesenchymal transition in rat adult male offspring

Studies have shown that adult offspring of mothers fed a protein-restricted diet during pregnancy present a pronounced reduction of nephron number associated with decreased fractional urinary sodium excretion and arterial hypertension. Additionally, recent advances in our understanding of the molecular pathways that govern the association of gestational nutritional restriction, intrauterine growth retardation and inflammation with impaired nephrogenesis, nephron underdosing and kidney fibrosis point to the epithelial to mesenchymal transition (EMT) as a common factor. In the current study, protein and sodium urinary excretion rates were evaluated in rats, and immunohistochemistry and western blot techniques were used to characterize kidney structure changes in 16 week old male offspring of mothers fed a low-protein diet during pregnancy (LP group) compared with age-matched (NP) controls. We also verified the expression of miRNA, mRNA and protein markers of fibrosis and the EMT in whole kidney prepared from LP offspring. We found, surprisingly, that arterial hypertension and long-term hyperfiltration, manifest by proteinuria, were associated with increased renal miR-192 and miR-200 family expression in 16 week old LP relative to age-matched NP rats. Measurement of kidney fibrosis and EMT-related protein markers, by histochemistry and immunoblot techniques, showed a significant rise of TGF-β1 and type-I collagen content in glomeruli and tubulointerstitial areas, accompanied by enhanced fibronectin and ZEB1 and decreased E-cadherin immunoreactivity in 16 week old LP offspring. The results were partially confirmed by increased gene (mRNA) expression of collagen 1α1, collagen 1α2 and ZEB1 in LP whole kidneys compared with those of age-matched NP offspring. In view of the presumed functional overload in the remaining nephrons, we suggest that hypertension and proteinuria development following maternal protein restriction may be a preponderant factor for EMT and structural kidney changes in LP offspring. However, our study was not wholly able to establish the precise role of miRNAs in LP kidney disorders. Thus, further studies will be required to assess the contribution of the miR family to renal injury in a gestational protein-restricted model of fetal programming.

Safety and effectiveness of low-protein diet supplemented with ketoacids in diabetic patients with chronic kidney disease

BACKGROUND

The impact of the low-protein diet on nutrition in CKD diabetics is uncertain.

METHODS

The metabolic and nutritional effects of a low-protein (0.5-0.6 g/kg/d), normal-high energy (30-35 kcal/kg/d) diet supplemented with ketoacids (LPD-KA) were prospectively evaluated in CKD patients with (DM) and without (non-DM) diabetes mellitus.

RESULTS

197 patients on CKD stages 3-5 were enrolled. DM (n = 81) and non-DM (n = 116) were comparable for gender (Male 58 vs 55%), age (66 ± 9 vs 63 ± 18 years), renal function (eGFR 23 ± 13 vs 24 ± 13 mL/min). After 6-month, serum urea (DM: 131 ± 58 to 105 ± 49 mg/dl, p < 0.05; non-DM: 115 ± 52 to 88 ± 36, p < 0.05) and phosphate (DM: 4.5 ± 1.3 to 4.1 ± 1.2 mg/dl, p = 0.06; non-DM: 4.3 ± 1.0 to 3.7 ± 0.8, p < 0.05) declined. Fasting glucose decreased in DM (126 ± 52 to 103 ± 29 mg/dl, p < 0.05) without insulin dose increase. These effects were preserved after 3-year. Serum albumin did not change after 6 months (DM: 3.7 ± 0.6 to 3.8 ± 0.4 mg/dl; non-DM: 4.0 ± 0.6 to 4.0 ± 0.4) and in the long-term. Body weight (BW) declined after the diet start (DM: 68.9 ± 14.3 to 65.1 ± 12.1 kg, p < 0.05; non-DM: 66.6 ± 15.1 to 64.1 ± 15.1, p < 0.05) and was stable at 6 months and 3 years. Muscle strength at baseline was reduced in all patients and remained stable during the diet period. Changes of nutritional markers during the study were similar among groups and diabetes was not associated to any nutritional change at the multivariate analysis. As attain wasting, lower BMI (< 23 kg/m²) and albumin (< 3.8 g/dl) levels were present in 1/3 patients at start and along 3 years, cholesterol never dropped below the lower threshold (< 100 mg/dl) and poorer FM (< 10%) was less than 10% during the study in both groups.

CONCLUSIONS

In diabetic CKD patients a low-protein diet supplemented with ketoacids improves uremia and diabetes, causes sudden decline of body weight which remains stable over time and has not a negative effect on wasting and muscle mass and fitness. In diabetic CKD patients the LPD-KA is safe and the nutritional impact is the same as in non-diabetics CKD.

Low-protein diet for conservative management of chronic kidney disease: a systematic review and meta-analysis of controlled trials

BACKGROUND

Recent data pose the question whether conservative management of chronic kidney disease (CKD) by means of a low-protein diet can be a safe and effective means to avoid or defer transition to dialysis therapy without causing protein-energy wasting or cachexia. We aimed to systematically review and meta-analyse the controlled clinical trials with adequate participants in each trial, providing rigorous contemporary evidence of the impact of a low-protein diet in the management of uraemia and its complications in patients with CKD.

METHODS

We searched MEDLINE (PubMed) and other sources for controlled trials on CKD to compare clinical management of CKD patients under various levels of dietary protein intake or to compare restricted protein intake with other interventions. Studies with similar patients, interventions, and outcomes were included in the meta-analyses.

RESULTS

We identified 16 controlled trials of low-protein diet in CKD that met the stringent qualification criteria including having 30 or more participants. Compared with diets with protein intake of >0.8 g/kg/day, diets with restricted protein intake (<0.8 g/kg/day) were associated with higher serum bicarbonate levels, lower phosphorus levels, lower azotemia, lower rates of progression to end-stage renal disease, and a trend towards lower rates of all-cause death. In addition, very-low-protein diets (protein intake <0.4 g/kg/day) were associated with greater preservation of kidney function and reduction in the rate of progression to end-stage renal disease. Safety and adherence to a low-protein diet was not inferior to a normal protein diet, and there was no difference in the rate of malnutrition or protein-energy wasting.

CONCLUSIONS

In this pooled analysis of moderate-size controlled trials, a low-protein diet appears to enhance the conservative management of non-dialysis-dependent CKD and may be considered as a potential option for CKD patients who wish to avoid or defer dialysis initiation and to slow down the progression of CKD, while the risk of protein-energy wasting and cachexia remains minimal.

Very low-protein diet to postpone renal failure: Pathophysiology and clinical applications in chronic kidney disease

The uremic syndrome is a metabolic disorder characterized by the impairment of renal handling of several solutes, the resulting accumulation of toxic products and the activation of some adaptive but detrimental mechanisms which all together contribute to the progression of renal damage. In moderate to advanced renal failure, the dietary manipulation of nutrients improves metabolic abnormalities and may contribute to delay the time of dialysis initiation. This commentary focuses on the physiopathological rationale and the clinical application of the very low-protein diet supplemented with ketoanalogs for the management of chronic kidney disease.

A low-protein diet exerts a beneficial effect on diabetic status and prevents diabetic nephropathy in Wistar fatty rats, an animal model of type 2 diabetes and obesity

Background

The objective of this study is to investigate the effects of a low-protein diet (LPD) starting from a young age on diabetic status and renal injury in a rat model of type 2 diabetes and obesity.

Methods

Diabetic male Wistar fatty (fa/fa) rats (WFRs) were fed a standard diet (23.84% protein) or an LPD (5.77% protein) for 24 weeks beginning at 6 weeks of age. We investigated the effects of the LPD on total body weight (BW); fat weight (FW); lower-limb muscle weight (MW); several measures of diabetic status, including fasting/random glucose levels, HOMA-IR and the IPITT; and renal injuries, including renal hypertrophy, albuminuria and histological changes. Additionally, autophagy and activation of mTORC1 were evaluated in the diabetic renal cortex. Furthermore, plasma FGF21 and high-molecular-weight (HMW) adiponectin levels, as well as UCP1 expression levels in brown adipose tissue (BAT), were evaluated.

Results

Increases in BW and FW in WFRs were significantly reduced by the LPD, and the LPD resulted in a significant reduction of lower-limb MW in WFRs. The LPD suppressed the elevation of glucose levels in WFRs through improvement of insulin resistance. The LPD also elevated the plasma FGF21 and HMW adiponectin of WFRs, as well as UCP1 expression in the BAT of the animals. Renal hypertrophy, albuminuria, renal histological changes, and increased expression of p62 and phospho-S6 ribosomal protein (p-S6RP) were observed in WFRs compared with the values from WLRs. The LPD clearly prevented the diabetic kidneys from sustaining any damage.

Conclusions

The LPD prevented the progression of diabetic status; this effect may have been associated with the reduction of FW and the elevation of plasma FGF21 and HMW adiponectin, as well as UCP1 expression in BAT, resulting in suppression of diabetic nephropathy. However, MW was decreased in rats by the consumption of an LPD from a young age; therefore, further research is needed to resolve the nutritional issue of LPD on decreasing in MW.

Red meat intake in chronic kidney disease patients: Two sides of the coin

Red meat is an important dietary source of high biological value protein and micronutrients such as vitamins, iron, and zinc that exert many beneficial functions. However, high consumption of animal protein sources, especially red meat, results in an increased intake of saturated fat, cholesterol, iron, and salt, as well as an excessive acid load. Red meat intake may lead to an elevated production of uremic toxins by the gut microbiota, such as trimethylamine n-oxide (TMAO), indoxyl sulfate, and p-cresyl sulfate. These uremic toxins are associated with increased risk for cardiovascular (CV) mortality. Limiting the intake of red meat in patients with chronic kidney disease (CKD) thus may be a good strategy to reduce CV risk, and may slow the progression of kidney disease. In the present review, we discuss the role of red meat in the diet of patients with CKD. Additionally, we report on a pilot study that focused on the effect of a low-protein diet on TMAO plasma levels in nondialysis CKD patients.

Branched-chain amino acid supplementation restores reduced insulinotropic activity of a low-protein diet through the vagus nerve in rats

Background

Previously, we reported that a low-protein diet significantly reduced insulin secretion in response to feeding within 1 h in rats, suggesting that the insulinotropic effect of dietary protein plays an important role in maintaining normal insulin release. The current study aimed to elucidate whether deficiency of certain amino acids could diminish the insulinotropic activity and to investigate whether reduced insulin secretion in response to a low-protein diet is restored by supplementation with certain amino acids.

Methods

First, we fed male Wistar rats (5–6 rats per group) with diets deficient in every single amino acid or three branched-chain amino acids (BCAAs); within 1–2 h after the onset of feeding, we measured the plasma insulin levels by using an enzyme-linked immunosorbent assay (ELISA). As insulin secretion was reduced in BCAA-deficient groups, we fed low-protein diets supplemented with BCAAs to assess whether the reduced insulin secretion was restored. In addition, we treated the pancreatic beta cell line MIN6 with BCAAs to investigate the direct insulinotropic activity on beta cells. Lastly, we investigated the effect of the three BCAAs on sham-operated or vagotomized rats to assess involvement of the vagus nerve in restoration of the insulinotropic activity.

Results

Feeding a low-protein diet reduced essential amino acid concentrations in the plasma during an absorptive state, suggesting that reduced plasma amino acid levels can be an initial signal of protein deficiency. In normal rats, insulin secretion was reduced when leucine, valine, or three BCAAs were deficient. Insulin secretion was restored to normal levels by supplementation of the low-protein diet with three BCAAs, but not by supplementation with any single BCAA. In MIN6 cells, each BCAA alone stimulated insulin secretion but the three BCAAs did not show a synergistic stimulatory effect. The three BCAAs showed a synergistic stimulatory effect in sham-operated rats but failed to stimulate insulin secretion in vagotomized rats.

Conclusions

Leucine and valine play a role in maintaining normal insulin release by directly stimulating beta cells, and supplementation with the three BCAAs is sufficient to compensate for the reduced insulinotropic activity of the low-protein diet, through the vagus nerve.

Effect of oregano essential oil and benzoic acid supplementation to a low-protein diet on meat quality, fatty acid composition, and lipid stability of longissimus thoracis muscle in pigs

Background

Consumers are becoming increasingly interested in food containing appropriately high concentration of intramuscular fat (IMF) and polyunsaturated fatty acids (PUFA). The supplementation of feed with antioxidants decreases degradation of lipids in muscles thereby enhances nutritional and sensory properties of meat. Two experiments were conducted to determine the effects of adding oregano essential oil (OEO) and benzoic acid (BA) to low-protein, amino acid-supplemented diets on meat quality, sensory profile, fatty acid composition, and lipid oxidation of longissimus thoracis (LT) muscle in pigs.

Methods

In Exp. 1, 21 barrows were housed in metabolism cages and randomly allotted to 1 of 3 diets. The three diets were normal protein diet (NPD), medium protein diet (MPD) and low protein diet (LPD) with 1% and 2% less than NPD, respectively. In Exp. 2, 36 barrows were randomly divided into three experimental groups, namely, NPD, LPD, and identical LPD supplemented with blends of OEO (250 mg/kg feed) and BA (1000 mg/kg feed) (LPOB) groups.

Results

No significant effects of diets on meat quality were observed in Exp. 1. The b*_45min, tenderness, and IMF content in LPD muscle were higher than those in NPD and LPOB muscle. The LT muscle in LPD group contained a higher percentage of oleic acid (C18:1n-9) and a lower percentage of linoleic acid (C18:2n-6) than those in NPD group. Dietary LPOB improved oxidative stability, total superoxide dismutase, and glutathione peroxidase but decreased drip loss in LT muscle.

Conclusions

These findings suggest that growing-finishing pigs fed with a low-protein, amino acid-supplemented diet show a high content of intramuscular fat in the longissimus thoracis muscle. Dietary LPOB enhances the anti-oxidative status by improving antioxidative capacity but deteriorates the sensory attributes by decreasing IMF content of meat.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-017-0535-1) contains supplementary material, which is available to authorized users.

miR-124a expression contributes to the monophasic pattern of insulin secretion in islets from pregnant rats submitted to a low-protein diet

PURPOSE

To evaluate the role of miR-124a in the regulation of genes involved in insulin exocytosis and its effects on the kinetics of insulin secretion in pancreatic islets from pregnant rats submitted to a low-protein diet.

METHODS

Adult control non-pregnant (CNP) and control pregnant (CP) rats were fed a normal protein diet (17%), whereas low-protein non-pregnant (LPNP) and low-protein pregnant (LPP) rats were fed a low-protein diet (6%) from days 1 to 15 of pregnancy. Kinetics of the glucose-induced insulin release and measurement of [Ca²⁺]_i in pancreatic islets were assessed by standard protocols. The miR-124a expression and gene transcriptions from pancreatic islets were determined by real-time polymerase chain reaction.

RESULTS

In islets from LPP rats, the first phase of insulin release was abrogated. The AUC [Ca²⁺]_i from the LPP group was lower compared with the other groups. miR-124a expression was reduced by a low-protein diet. SNAP-25 mRNA, protein expression, and Rab3A protein content were lower in the LPP rats than in CP rats. Syntaxin 1A and Kir6.2 mRNA levels were decreased in islets from low-protein rats compared with control rats, whereas their protein content was reduced in islets from pregnant rats.

CONCLUSIONS

Loss of biphasic insulin secretion in islets from LPP rats appears to have resulted from reduced [Ca²⁺]_i due, at least in part, to Kir6.2 underexpression and from the changes in exocytotic elements that are influenced either directly or indirectly by miR-124a.

Amino acid starvation-induced autophagy is involved in reduced subcutaneous fat deposition in weaning piglets derived from sows fed low-protein diet during gestation and lactation : Autophagy is involved in reduced fat deposition in maternal low-protein piglets

PURPOSE

The study aimed to determine the effects of maternal low-protein (LP) diet on subcutaneous fat deposition of weaning piglets and the potential mechanism.

METHODS

Sows were fed either a standard protein (SP, 15 and 18% crude protein) or a LP diet (50% protein levels of SP) throughout pregnancy and lactation. Subcutaneous fat and blood were sampled from male piglets at 28 days of age. Serum biochemical metabolites and hormone concentrations were detected with the enzymatic colorimetric methods. Serum-free amino acid (FAA) levels were measured by amino acid auto-analyzer. The mRNA and protein were measured by qRT-PCR and Western blot.

RESULTS

Body weight, back fat thickness, triglycerides concentrations in subcutaneous fat tissue, and serum, as well as FFA concentrations were significantly reduced in LP piglets when compared with SP piglets. Further studies showed that mRNA and protein expression of acetyl-CoA carboxylase and fatty acid synthetase, two key enzymes of de novo lipogenesis, were significantly reduced in LP piglets, while mRNA expression and the lipolytic enzymes activities of lipolysis genes, adipose triglyceride lipase and hormone-sensitive lipase, were significantly increased. Furthermore, expression of autophagy-related gene 7 and autophagy maker gene microtubule-associated protein 1A/1B-light chain 3 (LC 3) as well as the conversion of LC3I to LC3II were significantly elevated, along with the expression of activating transcription factor-4 and eukaryotic translation initiation factor-2a.

CONCLUSION

These results indicate that amino acid starvation-induced autophagy is involved in reduced subcutaneous fat deposition in maternal LP weaning piglets, demonstrating links between maternal protein restriction and offspring fat deposition.

Low-protein diet supplemented with ketoacids ameliorates proteinuria in 3/4 nephrectomised rats by directly inhibiting the intrarenal renin-angiotensin system

Low-protein diet plus ketoacids (LPD+KA) has been reported to decrease proteinuria in patients with chronic kidney diseases (CKD). However, the mechanisms have not been clarified. As over-activation of intrarenal renin-angiotensin system (RAS) has been shown to play a key role in the progression of CKD, the current study was performed to investigate the direct effects of LPD+KA on intrarenal RAS, independently of renal haemodynamics. In this study, 3/4 subtotal renal ablated rats were fed 18 % normal-protein diet (Nx-NPD), 6 % low-protein diet (Nx-LPD) or 5 % low-protein diet plus 1 % ketoacids (Nx-LPD+KA) for 12 weeks. Sham-operated rats fed NPD served as controls. The level of proteinuria and expression of renin, angiotensin II (AngII) and its type 1 receptors (AT1R) in the renal cortex were markedly higher in Nx-NPD group than in the sham group. LPD+KA significantly decreased the proteinuria and inhibited intrarenal RAS activation. To exclude renal haemodynamic impact on intrarenal RAS, the serum samples derived from the different groups were added to the culture medium of mesangial cells. It showed that the serum from Nx-NPD directly induced higher expression of AngII, AT1R, fibronectin and transforming growth factor-β1 in the mesangial cells than in the control group. Nx-LPD+KA serum significantly inhibited these abnormalities. Then, proteomics and biochemical detection suggested that the mechanisms underlying these beneficial effects of LPD+KA might be amelioration of the nutritional metabolic disorders and oxidative stress. In conclusion, LPD+KA could directly inhibit the intrarenal RAS activation, independently of renal haemodynamics, thus attenuating the proteinuria in CKD rats.

"Dietaly": practical issues for the nutritional management of CKD patients in Italy

Evidence exists that nutritional therapy induces favorable metabolic changes, prevents signs and symptoms of renal insufficiency, and is able to delay the need of dialysis. Currently, the main concern of the renal diets has turned from the efficacy to the feasibility in the daily clinical practice.Herewith we describe some different dietary approaches, developed in Italy in the last decades and applied in the actual clinical practice for the nutritional management of CKD patients.A step-wise approach or simplified dietary regimens are usually prescribed while taking into account not only the residual renal function and progression rate but also socio-economic, psychological and functional aspects.The application of the principles of the Mediterranean diet that covers the recommended daily allowances for nutrients and protein (0.8 g/Kg/day) exert a favorable effect at least in the early stages of CKD. Low protein (0.6 g/kg/day) regimens that include vegan diet and very low-protein (0.3-0.4 g/Kg/day) diet supplemented with essential amino acids and ketoacids, represent more opportunities that should be tailored on the single patient's needs.Rather than a structured dietary plan, a list of basic recommendations to improve compliance with a low-sodium diet in CKD may allow patients to reach the desired salt target in the daily eating.Another approach consists of low protein diets as part of an integrated menu, in which patients can choose the "diet" that best suits their preferences and clinical needs.Lastly, in order to allow efficacy and safety, the importance of monitoring and follow up of a proper nutritional treatment in CKD patients is emphasized.

A very-low-protein diet ameliorates advanced diabetic nephropathy through autophagy induction by suppression of the mTORC1 pathway in Wistar fatty rats, an animal model of type 2 diabetes and obesity

AIMS/HYPOTHESIS

The efficacy of a low-protein diet (LPD) on diabetic nephropathy is controversial. We aimed to investigate the renoprotective effects of an LPD and the underlying molecular mechanism in a rat model of type 2 diabetes and obesity.

METHODS

Diabetic male Wistar fatty (fa/fa) rats (WFRs) were treated with a standard diet (23.84% protein) or an LPD (5.77% protein) for 20 weeks from 24 weeks of age. We investigated the effect of the LPD on renal function, fibrosis, tubular cell damage, inflammation, mitochondrial morphology of proximal tubular cells (PTCs), apoptosis, autophagy and activation of mammalian target of rapamycin complex 1 (mTORC1).

RESULTS

Kidney weight, albuminuria, excretion of urinary liver-type fatty acid binding protein, levels of plasma cystatin C and changes in renal histology, including fibrosis, tubular cell damage and inflammation, were aggravated in WFRs compared with non-diabetic Wistar lean rats (WLRs). Fragmented and swelling mitochondria accumulated in PTCs and apoptosis were enhanced in the kidney of WFRs. Immunohistochemical staining of p62 and p-S6 ribosomal protein (p-S6RP) in the tubular lesions of WFRs was increased compared with WLRs. The LPD intervention clearly ameliorated damage as shown by the assessment of renal function and histology, particularly tubulointerstitial damage in diabetic kidneys. Additionally, the 5.77% LPD, but not the 11.46% LPD, significantly suppressed p-S6RP levels and increased microtubule-associated protein light chain 3-II levels in the renal cortex. The LPD intervention partially decreased HbA1c levels in WFRs, and no differences in mean BP were observed among any of the groups.

CONCLUSIONS/INTERPRETATION

A very-low-protein diet improved advanced diabetic renal injuries, including tubulointerstitial damage, by restoring autophagy through the suppression of the mTORC1 pathway.

6-tips diet: a simplified dietary approach in patients with chronic renal disease. A clinical randomized trial

BACKGROUND

The beneficial effects of dietary restriction of proteins in chronic kidney disease are widely recognized; however, poor compliance to prescribed low-protein diets (LPD) may limit their effectiveness. To help patients to adhere to the dietary prescriptions, interventions as education programmes and dietary counselling are critical, but it is also important to develop simple and attractive approaches to the LPD, especially when dietitians are not available. Therefore, we elaborated a simplified and easy to manage dietary approach consisting of 6 tips (6-tip diet, 6-TD) which could replace the standard, non-individualized LPD in Nephrology Units where dietary counselling is not available; hence, our working hypothesis was to evaluate the effects of such diet vs a standard moderately protein-restricted diet on metabolic parameters and patients' adherence.

METHODS

In this randomized trial, 57 CKD patients stage 3b-5 were randomly assigned (1:1) to receive the 6-TD (Group 6-TD) or a LPD containing 0.8 g/kg/day of proteins (Group LPD) for 6 months. The primary endpoint was to evaluate the effects of the two different diets on the main "metabolic" parameters and on patients' adherence (registration number NCT01865526).

RESULTS

Both dietary regimens were associated with a progressive reduction in protein intake and urinary urea excretion compared to baseline, although the decrease was more pronounced in Group 6-TD. Effects on serum levels of urea nitrogen and urinary phosphate excretion were greater in Group 6-TD. Plasma levels of phosphate, bicarbonate and PTH, and urinary NaCl excretion remained stable in both groups throughout the study. 44 % of LPD patients were adherent to the dietary prescription vs 70 % of Group 6-TD.

CONCLUSIONS

A simplified diet, consisting of 6 clear points easily managed by CKD patients, produced beneficial effects either on the metabolic profile of renal disease and on patients' adherence to the dietary plan, when compared to a standard LPD.

Protein-energy malnutrition at mid-adulthood does not imprint long-term metabolic consequences in male rats

PURPOSE

The long-term effects of the development of chronic metabolic diseases such as type 2 diabetes and obesity have been associated with nutritional insults in critical life stages. In this study, we evaluated the effect of a low-protein diet on metabolism in mid-adulthood male rats.

METHODS

At 90 days of age, Wistar male rats were fed a low-protein diet (4.0 %, LP group) for 30 days, whereas control rats were fed a normal-protein diet (20.5 %, NP group) throughout their lifetimes. To allow for dietary rehabilitation, from 120 to 180 days of age, the LP rats were fed a normal-protein diet. Then, we measured body composition, fat stores, glucose-insulin homeostasis and pancreatic islet function.

RESULTS

At 120 days of age, just after low-protein diet treatment, the LP rats displayed a strong lean phenotype, hypoinsulinemia, as assessed under fasting and glucose tolerance test conditions, as well as weak pancreatic islet insulinotropic response to glucose and acetylcholine (p < 0.01). At 180 days of age, after poor-protein diet rehabilitation, the LP rats displayed a slight lean phenotype (p < 0.05), which was associated with a high body weight gain (p < 0.001). Additionally, fat pad accumulation, glycemia and insulinemia, as well as the pancreatic islet insulinotropic response, were not significantly different between the LP and NP rats (p > 0.05).

CONCLUSIONS

Taken together, the present data suggest that the effects of dietary restriction as a stressor in adulthood are reversible with dietary rehabilitation, indicating that adulthood is not a sensitive or critical time window for metabolic programming.

Low-protein diet fed to crossbred sows during pregnancy and lactation enhances myostatin gene expression through epigenetic regulation in skeletal muscle of weaning piglets

PURPOSE

This study was aimed to investigate the effects of a maternal low-protein diet on transcriptional regulation of the myostatin (MSTN) gene in skeletal muscle of weaning piglets.

METHODS

Sows were fed either a standard-protein (SP, 15 and 18 % crude protein) or a low-protein (LP, 50 % protein level of SP) diet throughout pregnancy and lactation. Longissimus dorsi muscle was sampled from male piglets at 28 days of age. The mRNA was determined by RT-PCR, and protein was measured by Western blot. Chromatin immunoprecipitation assay was used to determine the binding of transcription factors and histone H3 modifications on the MSTN gene promoter.

RESULTS

The maternal LP diet significantly decreased body weight and average daily gain (P < 0.05), which was associated with significantly lower plasma concentration of urea nitrogen and total protein (P < 0.05), as well as decreased muscle RNA content (P < 0.05). MSTN mRNA (P < 0.05) was significantly increased, together with enhanced (P < 0.05) mRNA and protein expression of forkhead box class O family member protein 3 (FoxO3), and a tendency of an increase (P = 0.10) in glucocorticoid receptor (GR) mRNA in the muscle of LP piglets. Furthermore, the binding of both FoxO3 and GR to the MSTN gene promoter was significantly higher (P < 0.05) in muscle of LP piglets, together with significantly enriched (P < 0.05) gene activation markers, H3K9Ac and H3K4me3.

CONCLUSION

These results indicate that MSTN mediates maternal LP diet-induced growth retardation, through epigenetic regulation involving FoxO3 and GR binding to its promoter.